Host and host age preference of Trichogramma galloi and T. pretiosum (Hymenoptera: Trichogrammatidae) reared on different hosts

Host and host age preference of Trichogramma galloi and T. pretiosum (Hymenoptera: Trichogrammatidae) reared on different hosts

Monje, J.C.; Zebitz, C.P.W.; Ohnesorge, B.

Journal of Economic Entomology 92(1): 97-103

1999

Experiments were conducted to investigate the host and host age preference of Trichogramma galloi Zucchi and T. pretiosum Riley when reared from the eggs of Diatraea rufescens Box (Lepidoptera: Pyralidae), D. saccharalis F., or Sitotroga cerealella Olivier (Lepidoptera: Gelechiidae). The effect of the host on host preference was weak or absent, because the majority of the test females of both Trichogramma species attacked eggs of a certain host first. T. galloi females did not recognize eggs of S. cerealella as a potential host, suggesting that females of this species need additional olfactory cues for host recognition. Furthermore, relative host size had a noticeable effect on choice of the first host by T. galloi. The larger eggs of D. rufescens were preferred over eggs of D. saccharalis. This was not the same for females of T. pretiosum; the majority of them attacked the small eggs of S. cerealella first. Eggs of B. rufescens were accepted to a lesser extent and eggs of B. saccharalis were rejected. In choice experiments, females of T. galloi consistently preferred younger eggs of B. rufescens over older ones. In nonchoice situations, only 4-d-old host eggs were parasitized less commonly by both T. galloi and T. pretiosum and had a lower number of progeny allocated to them. Five-day-old hosts were never parasitized. Nevertheless, there was a clear-cut relation between host age and time lapse before the 1st host acceptance. The implications of these results for learning in Trichogramma and for candidate species selection in biological control are discussed.